Forget about standover height and seat tube length. Who cares how many inches your nads are above your frame when you are standing over your bike? Use the (horizontal) top tube length as your main criterion for frame size. I have frames with c-c seat tube lengths ranging from 62 cm to 58 cm. All of them have 57.5 cm top tubes with 110 mm stems and all of them fit essentially the same. You can make minor adjustments with stem length, stem angle, headset spacers, bar type, and saddle position. But first you want a frame in your range of fit. Chances are very likely that frames with your tob tube length will have a standover that varies as much as 4-5 cm, you will probably be able to standover all of them. The most important size criteria are the relationship between saddle, bars, and bottom bracket. You'll have a better chance of getting a frame thats within your fit-range if you size by top tube length.